Dead and dying fish — suckers, northern pike and walleye — founder in a small pocket of open water along the shore of North Center Lake near Lindstrom, Minn., around the second week of March 2013. The Department of Natural Resources suspects the lake suffered “a significant winterkill” from a lack of dissolved oxygen, a rarity for the deep lake. With its early and persistent blanketing of snow, this winter is likely to be especially prone for winterkills, a natural phenomenon. Photo courtesy of Mike Waters.

For much of Minnesota, this has been a good one — meaning a bad one — for winter fish kills.

An early freeze, followed by a thick and persistent blanket of sun-blocking snow, increased the odds that shallow lakes prone to winter fish kills would face the naturally occurring purge, according to state biologists.

But a “significant” kill on at least one deeper lake — North Center Lake near Lindstrom — suggests this could be one of the worst in decades.

“It’s pretty sad,” said Mike Waters, a resident of about 30 years along North Center, a 749-acre lake in Chisago County known for good fishing for bass, walleye, crappies and northern pike — all of which might have been killed off in large numbers. “I don’t know what to think because I’ve never seen it before.”

Records from the Minnesota Department of Natural Resources list only two recorded winterkills, in the 1950s and in the 1960s. The lake has depths greater than 40 feet and is connected to South Center Lake by a navigable channel.

Shallow lakes are most prone to winterkills, a natural phenomenon in which a lack of sunlight reaching the water indirectly causes oxygen levels to plummet, suffocating fish.

To be clear, no one knows for sure how severe any winter fish kills are until the ice is out and fisheries biologists can conduct spring netting surveys. Lakes with severe kills will be stocked, per each lake’s management plan.

Mid- to late winter, before the thaw, is generally the time of year when oxygen levels are lowest. That time has passed, and melting snow already is allowing oxygen levels to rise on lakes.

Winterkills can be a boon for fishing, because a blank slate of a lake can produce bumper crops of game fish, several DNR officials said. But they also know a strong kill can make for poor, or even pointless, fishing the following year.

“I’ll be honest: Our guys are nervous,” said Jack Lauer, regional fisheries manager for the DNR’s Region 4, which encompasses the southwest part of the state. The region has numerous winterkill-prone shallow lakes.

“They will not be surprised if they get in there and find out in some of these lakes, yep, there’s nothing much left,” Lauer said.

Deep lakes in northern Minnesota are by and large immune to widespread winterkills, although some brook trout lakes in the Arrowhead have been known to experience them.

In much of Lauer’s territory, the season was shaping up to be a kill-fest before the dead of winter. Oxygen levels were already “the worst in seven or eight years” when DNR workers took readings. However, the levels appeared to plateau, Lauer said, and much of the snow that shrouded other parts of the state either didn’t fall or was blown off ice-covered lakes in the west-central region.

“We really don’t know whether a lot of these lakes had kills or not,” he said.

But the list of known casualties has grown. In addition to smaller lakes prone to winterkills, the list includes:

— Albert Lea Lake in Albert Lea: Officials have turned off an aeration system designed to reduce winterkills. The thinking is this: Rather than fight fate — the aerator was losing ground — and risk a partial kill of all but carp and bullheads, let the kill be complete and look toward stocking in the spring.

— Pelican Lake in Wright County: This winter, officials — thinking that the fish population’s days were numbered from low oxygen levels — lifted nearly all manner of fishing restrictions. In fact, Pelican’s days are numbered anyway; the lake is scheduled to be drained to restore it as prime duck-breeding habitat.

— Knife Lake near Mora: In the face of a likely strong winterkill on the 1,260-acre lake, a new aeration system was activated for the first time. Officials aren’t sure whether it’ll be enough.

And then there’s North Center, where low water levels are suspected of exacerbating the wintry conditions.

Waters said he knew things were bad when he recently was ice fishing in 12 feet of water.

“The water is clearer than it’s ever been, and I could see clear to the bottom,” he said. “There was a big dead sunfish laying down there and nothing else around. Then this little crappie came fluttering along and swam up my ice hole. I couldn’t get it to go back down the hole. It was looking for oxygen. That’s when I knew we’d be in trouble.”

Dead fish started showing up March 11 at several spots on the lake where residences with geothermal heating systems pump out warm water, which melts shoreline ice. In the case of Waters’ house, the discharge is at least 35 feet from the water’s edge. A pool of open water formed before — and above — the actual lakeshore.

“To get there, those fish would have had to burrow under the ice and snow, pretty much through the sand,” he said. “One day, it was just loaded with fish. A lot of suckers were dead. I must have pulled out 150 with a pitchfork, and then I saw walleye and pike. Some of the pike underneath were still alive.”

The apparently desperate uphill swim for oxygenated waters led to a gory cage match of predator and prey in the tiny pool.

“All these fish were packed in there, and the pike were still trying to eat. I saw one bullhead swimming around that was bit in half,” Waters said.

On another part of the lake, a mass of dead carp and bullhead — the two species most likely to survive a winterkill — obscured dead walleyes, largemouth bass and pike.

Two days later, technicians from the DNR measured saturated oxygen levels in five places on the lake.

If indeed the kill is as complete as some fear, the DNR will respond by stocking relatively small numbers — perhaps 100 — prespawn adult bluegill, perch, crappies, bass and pike netted from South Center Lake in the spring. In addition, walleye fry from rearing ponds will be introduced in the spring and fingerlings in the fall. (Natural reproduction of walleyes is minimal in North Center.)

Roger Hugill, the manager of the DNR’s Hinckley-based area, said he’s not ready to write off the lake for this season.

“You never know,” Hugill said. “It’s amazing what fish can find around the edges. Oxygen levels are rarely uniform, and if there are pockets of water with more oxygen, fish can find them.”

A local guru unwilling to write the lake off is Frank Dusenka, owner of Frankie’s Live Bait and Marine in Chisago City. He said a commercial fisherman with sonar that can peer 900 feet had a look and saw nothing. But he’s still bullish.

“A lot of lakes around here have really low oxygen right now, so the fish can seem impossible to find, but they’re still there,” Dusenka said. “I know how to find them.”

He regularly supplies game fish, via a special license, for display tanks at the Northwest Sportshow, which runs Wednesday through March 30 at the Minneapolis Convention Center. Normally, netting for the show is easy pickings on local waters. But last week he found himself stumped on Chisago Lake.

“I told the boys, ‘We’re going fishing,’ ” Dusenka said, and he embarked on a run-and-gun hole-drilling frenzy to locate fish. He found them one day in the late afternoon. “They were just piled up there, seemed like all the fish in the lake,” he said.

“I know I could go out right now to North Center, and if you give me enough time to find them, I can catch plenty of fish. They’re still there.”

As outdoors editor for the Pioneer Press, Orrick fishes, paddles, hunts, skis and romps across the region while staying on top of outdoors news. When the occasion demands, he's also been known to cover topics ranging from politics to golf. He lives in St. Paul with his wife and son.​

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